Backpack



FIG. 1 is a front elevational view of a backpack showing our new design;

FIG. 2 is a left side elevational view thereof, the right side elevational view being a mirror image thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top, front, left side perspective view thereof;

FIG. 5 is a top, rear, right side perspective view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines illustrate portions of the backpack and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 